System, method, and composition for geothermal heat harvest

Abstract

A system, composition and method for controlling fracture grown in the extraction of geothermal energy from an underground formation includes (i) introducing a first fracking fluid into an underground formation; (ii) introducing a second fracking fluid into the underground formation; wherein the specific gravity of the second fracking fluid is different from the specific gravity of the first fracturing fluid, thereby controlling the growth of at least one fracture in a downward direction, and wherein the fracking fluid in at least one of steps (i) or (ii) contains proppant particles having a thermal conductivity contrast of at least 5.

What is claimed: 
     
       1. A method of controlling fracture growth in the extraction of geothermal energy from an underground formation, comprising;
 (i) introducing a first fracking fluid into an underground formation; 
 (ii) introducing a second fracking fluid into the underground formation; 
 wherein a specific gravity of the second fracking fluid is different from a specific gravity of the first fracking fluid, thereby controlling the growth of at least one fracture in a downward direction; 
 wherein the first fracking fluid and the second fracking fluid in at least one of steps (i) or (ii) contains proppant particles having a thermal conductivity contrast of at least 5; and, 
 wherein at least one of the first fracking fluid and the second fracking fluid is a Zinc Bromide brine mixed to a density which exceeds a fracture gradient of a formation to be fractured. 
 
     
     
       2. The method of  claim 1 , wherein the proppant particles having a thermal conductivity contrast of at least 5 comprise at least one of tin; graphite;
 aluminum; hematite; bauxite; diamond; gold; and silver. 
 
     
     
       3. The method of  claim 2 , wherein the proppant particles comprise at least one of tin; graphite; aluminum; hematite; and bauxite. 
     
     
       4. The method of  claim 3 , wherein the proppant particles comprise tin. 
     
     
       5. The method of  claim 1 , wherein the specific gravity of the second fracking fluid is varied by increasing and decreasing a pounds per gallon of proppant particles per gallon of a carrier fluid. 
     
     
       6. The method of  claim 1 , wherein the proppant particles have a specific gravity of at least 3.0. 
     
     
       7. The method of  claim 1 , wherein the proppant particles comprise a specific gravity such that the proppant particles one of a) sinks, b) is neutrally buoyant, and c) floats relative to density of a fluid being pumped during a fracture operation. 
     
     
       8. The method of  claim 1 , wherein a solid particulate weighting agent is added to the Zinc Bromide brine to increase a density of at least one of the first fracking fluid and the second fracking fluid. 
     
     
       9. The method of  claim 8 , wherein the solid particulate weighting agent is at least one of a Zinc Bromide salt; tin; graphite; aluminum; hematite;
 bauxite; diamond; gold; and silver. 
 
     
     
       10. The method of  claim 1 , wherein the Zinc Bromide brine is left in an open hole as at least one of a conductive and a convective fluid surroundscurrounding at least part of a downhole heat exchanger. 
     
     
       11. The method of  claim 7 , wherein the proppant particles are configured to settle around an outside diameter of a downhole heat exchanger to create a thermally conductive bed.